Impact of fixed implant prosthetics using the ‘all-on-four’ treatment concept on speech intelligibility, articulation and oromyofunctional behaviour

The purpose of this case control study is to determine the impact of screw-retained fixed cross-arch prostheses, supported by four osseointegrated implants, on articulation and oromyofunctional behaviour. Objective (acoustic analysis) and subjective assessment techniques were used to determine the overall intelligibility, phonetic characteristics and oromyofunctional behaviour at an average period of 7.3 months after placement of the fixed implant prosthesis in 15 patients and 9 age-matched controls with intact dentition and without prosthetic appliances. Overall satisfaction with the prosthesis was 87%, but 53% of the subjects mentioned an impact on speech. 87% of the subjects presented with one or more distortions of the consonants. The most common distortions were distortions of the sound /s/ (sigmatismus simplex, 40% and sigmatismus stridens, 33%), simplex /z/ (27%), insufficient frication of /ʃ/ (20%), /ʒ/ (20%), addental production of /d/ (20%), /t/ (20%) or /s/ sound (13%) and devoiced /d/ (7%). In the control group, no articulation disorders were noted. Oromyofunctional behaviour in both groups was normal. To what extent motor-oriented speech therapy (with focus on tongue function) immediately after periodontal treatment (after wound healing) would decrease the persistent phonetic distortions is a subject for further research.